Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by IC engines. Conventional exhaust gas aftertreatment systems include any of several different components to reduce the levels of harmful exhaust emissions present in exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a selective catalytic reduction (SCR) catalyst to convert NOx (NO and NO2 in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3).
In order to meet increasingly strict NOx emission requirements and regulations, the concentration of the NOx gas in the exhaust gas emerging from the SCR system is stringently measured and controlled to stay within the emission requirements. Some engines produce very large quantities of exhaust gas. Aftertreatment systems associated with such large engines often include multiple banks, branches or conduits. The exhaust gas is divided into smaller portions directed through each bank. Furthermore, multiple reductant insertions assemblies, including a number of injectors and or pumps are provided on each bank to inject large quantities of reductant into each bank to facilitate decomposition of constituents of the exhaust gas by the aftertreatment system. Multiple controllers are also included in such aftertreatment systems for controlling individual reductant insertion assemblies. However, this increases the complexity of the system, can lead to slow response to variable operating conditions of the aftertreatment system and eventually lead to increased emissions.